| Part 1 Experimental study of morphological changes of renal fibrosis by MRI-T2WIObjective: To evaluate the morphological changes of unilateral ureteral obstruction(UUO)rabbit model of renal fibrosis by T2 WI combined with pathological changesMethods: 40 New Zealand white rabbits were randomly divided into operation group(n=32)and sham operation group(n=8).The operation group underwent left ureteral ligation.In order to evaluate the dynamic changes of renal fibrosis with unilateral ureteral obstruction,coronal and axial T2 WI sequences were performed before and 2,4,6,8 weeks after modeling,respectively.Left kidney was taken for pathological examination after scanning,the thickness of the renal cortex D(cm)were measured at the maximum level of renal hilum.The renal cortex area A1(cm2)and renal parenchymal area A2(cm2)were measured at the maximum level of left renal hilum.Single-factor variance analysis was used to compare the A1 and A2 values of each time point before and after the modeling,linear regression analysis was used to compare the A1 and D values of each time point before and after modeling.Results: With the extension of the obstruction time,the degree of hydronephrosis gradually increased,the value of A1 was significantly increased after modeling in 2w,and gradually decreased in 4-8w(F=84.621,P<0.05).At the same time,the value of A2 decreased gradually(F=100.325,P<0.05).Pathology showed that with the obstruction time prolonged,the renal tubules of the rabbits in the operation group were significantly expanded in 2w after modeling.In 4-8w were gradually atrophic up to disappeared,and renal interstitial fibrosis,renal fibrosis gradually formed.Renal cortex is obvious thickening in 2w after the modeling,and gradually thinning in 4-8w,the linear regression analysis showed a strong and significant correlation between A1 and D values(F=485.669,P<0.05,R2=0.997).Conclusion: Unilateral ureteral obstruction can successfully establish a rabbit model of renal fibrosis.MRI-T2 WI can accurately reflect the morphological changes of the rabbit model of kidney fibrosis and provide an effective imaging method for clinical observation and diagnosis.Part 2 Quantitative assessment of renal fibrosis by MR Blood Oxygen Level-Dependent imagingObjective: To investigate the diagnostic value of blood oxygen level-dependent imaging(BOLD)in quantitative evaluation of renal fibrosis.Methods: 20 New Zealand white rabbits were randomly divided into operation group(n=16)and control group(n=4).The left ureter was completely ligated in the operation group and no treatment was performed in the control group.All rabbits were subjected to coronal T2 WI,axial T2 WI and axial BOLD scans before modeling and 2,4,6,8 weeks after modeling,respectively.Two rabbits of the operation group were randomly selected after MRI scan to perform pathological observation;the rabbits in the control group were sacrificed at 8w after scan to perform pathological observation.On the BOLD image,the R2* values of the renal cortex(C),medulla(M)and the same level muscle were measured separately.Calculate the standardized R2* values of the C and M,which respected to the s CR2*,s MR2*,s CR2* control,s MR2* control.Repeated measurement analysis of variance was used to compare the differences in s R2* at each time point between the operation group and the control group.The differences in s R2* in the operation group and the control group.The differences in s R2* between cortex and medulla at each time point between operation group and control group.Difference,P<0.05 was considered statistically significant.The correlation between s CR2*,s MR2* and fibrosis scores before and after modeling of left kidney was analyzed by linear regression analysis,P<0.05 was considered statistically significant.Results:The s CR2*values of the left kidney in the operation group at before and2,4,6,8 weeks after modeling were 0.55±0.02,0.46±0.03,0.56±0.01,0.68±0.02,0.75±0.03,respectively;while the values of s MR2*were 0.74±0.02,0.62±0.02,0.72±0.03,0.81±0.01,0.83±0.03,respectively.The s CR2*value of the left kidney in the operation group was statistically different before modeling and at 2,6,and 8 weeks after modeling(P values were 0.031,0.035,0.021,respectively);there was a statistically difference between the 2weeks and the 4,6,8 weeks after modeling(P values were 0.032,0.020,0.013,respectively);there was a statistically difference between the 4 weeks and the 6,8 weeks after modeling(P values were 0.037,0.019,respectively).The s MR2*value of the left kidney in the operation group was significantly different before modeling and at 2,6,and 8weeks after modeling(P values were 0.040,0.037,0.026,respectively);there was a statistically difference between the 2 weeks and the 4,6,and 8 weeks after modeling(P values were 0.038,0.025,0.017,respectively);there was a statistically differences between the 4 weeks and the 6,8 weeks after modeling(P values were 0.041,0.039,respectively).The s CR2*and s MR2*values in the operation group were statistically different before modeling and at 2,4,and 6 weeks after modeling(P values were 0.029,0.031,0.026,0.019,respectively).The s CR2*control values of the left kidney in the control group at before modeling and 2,4,6,and 8 weeks after modeling were 0.55±0.01,0.58±0.03,0.56±0.03,0.57±0.01,0.54±0.02,respectively;while the values of s MR2*control values were 0.74±0.03,0.73±0.01,0.72±0.03,0.70±0.02,0.74±0.01,respectively.The s CR2*control value and s MR2*control value of the left kidney in the control group had no statistical difference before and after the modeling(P>0.05).The s CR2*control value and s MR2*control values in the control group were statistically different before modeling and at 2,4,6 and 8 weeks after modeling(P values were 0.026,0.024,0.024,0.029,0.026,respectively).The values of s CR2*and s CR2*对照in the operation group and the control group were statistically different at the 2,6,8 weeks after modeling(P values were 0.029,0.040,0.037,respectively).The values of s MR2*and s MR2*对照in the operation group and the control group were statistically different at the 2,6,8 weeks after modeling(P values were 0.036,0.034,0.039,respectively).The pathology showed that the renal tubules expanded significantly in the 2th week after modeling,and gradually atrophied and disappeared in the 4th to 8th week.The glomeruli were swollen,degenerated and necrotic.The collagen fibers in renal interstitial increased gradually.The degree of blue staining in mesenchymal was gradually deepened and renal fibrosis gradually develops.The linear regression analysis showed a strong and significant correlation between values and the pathologic scores(R2=0.945,0.978,respectively).Conclusion: MR-BOLD can reflect the process of renal fibrosis and has certain value in evaluating renal fibrosis. |
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